More CNC Basics for Aluminum

Basic advice on cutting aluminum on CNC equipment. December 27, 2006

I'm pretty new to the CNC world - only been doing it for a little over a month. I'm working on a Komo Mach 1 with RouterCIM that my company recently purchased. I've gotten pretty familiar with it, using it mainly to CNC plywood, acrylic, PVC and the occasional aluminum. The only aluminum I've done thus far has been 1/6" thick stuff used in laminating. After a couple of tries, I was able to successfully run the job and have it look flawless... However, what I'm facing now is a little different. This new job consists of 1/4" diamond plate aluminum (unsure of grade). I plan on using a 3/8" downcut spiral O-flute solid carbide bit (Onsrud # 64-031), as this is the only bit I have available at the moment that is rated for aluminum.

Would it be a good idea to run this diamond plate in two or more passes or just one? What should I use to spray the tool in order to avoid overheating? Does my feed/rpm sound right? 12,000-13,000 rpm/150-200 feed rate?

Forum Responses
(CNC Forum)
From contributor D:
What are you doing? A through cut? A design milled in the surface? I would, myself, slow feed speed way down and make many very shallow passes, .005 or less, per pass. Though I could be way off.

From the original questioner:
Sorry for being vague... What I'm actually doing is a through cut logo (text).

From contributor W:
For 1/4" thick aluminum, I would suggest two rough passes and one finish pass. Always run the tool in the climb cutting direction, and coolant always helps. You will have to play with feed speeds to get the edge quality you need. Personally, I would use an upcut bit.

From contributor R:
Your tooling vendor should be able to tell you what feeds and speeds to use. Also, you will need to spray coolant on the tool while machining. Your tooling vendor should be able to give you some recommendations there as well. It would also be a good idea to talk with the folks at Komo.

From contributor G:
I would not use a down shear tool, as it will gum up. Use a straight or up shear tool, as you need the chips to come out of the cut. Both tools are for dry cutting.

From contributor T:
I hate to come in with a differing theory, but here goes. You should be using a solid carbide endmill for this application. Your depth of cut should not exceed one diameter of your cutting bit per pass. Endmills are always down cutting, as it helps to eliminate burs on the top surfaces.

Aluminum diamond plate is one of the harder grades of aluminum. It is used a great deal on running boards and other tough applications.

Based on this information, you can run this application at 12,000 RPM's and 76 inches per minute feed rate. This is a starting feed rate you can adjust up to increase production or down to improve finish quality.

As for coolant, if you want non-messy options, try stick wax or a cold air gun. If mess isn't an issue, most metalworking coolants will work, but some are made for non-ferrous metals as they will not stain the part.